The present invention relates to a new and improved construction of a support arrangement for a workpiece table of a gear testing machine which is mounted at a machine frame to be rotatable by means of an antifriction bearing arrangement about a vertical axis.
The support of such workpiece tables conventionally consists of an antifriction bearing arrangement which either is constituted by a combined radial-axial-bearing or composed of mutually separated axial bearings and radial bearings. The measuring accuracy of a gear testing machine, utilizing such workpiece table, among other things, depends upon the accuracy of the mounting and support of the workpiece table at the machine frame. The support of the workpiece table by means of the antifriction bearing or antifriction bearings thus must be free of play and radial deviation and axial deviation to a high degree. This requirement as well as the need for the workpiece table to be easily rotatable, and finally the fact that the workpiece table of a gear testing machine, in contrast to the workpiece table of machine tools, which during operation experience only negligibly small measuring forces, not however machining forces, has resulted in the workpiece table of gear testing machines being supported at relatively light antifriction bearing at the machine frame.
The invention is predicated upon the recognition that the antifriction bearings, especially axial bearings, and to a certain degree also however radial bearings, by means of which the workpiece table is supported at the machine frame, from time to time become suddenly overloaded by virtue of a rather harsh or non-gentle deposition of a heavy workpiece upon the workpiece table. This is especially true in the case of larger gear testing machines where the gears to be tested are deposited by means of a crane or the like upon the workpiece table. Here it is very difficult to avoid that the initial contact between the gear and the workpiece occurs rather extensively outside of the center of the table, with the result that the antifriction bearings are markedly eccentrically loaded. Eccentric loading of the bearings also can arise if the tested gear is again raised from the workpiece table by means of the crane. Such surge-like and/or eccentric loads can cause permanent deformation of the antifriction bearings, and therefore, can impair the measuring accuracy of the gear testing machine although the actual measuring equipment which is usually arranged at a machine frame is itself not exposed to such loads.